The pseudokinase Trib1 regulates the transition of exhausted T cells to a KLR CD8 effector state and its deletion improves checkpoint blockade.

T cell exhaustion (T ) impairs the ability of T cells to clear chronic infection or cancer. While exhausted T cells are hypofunctional, some exhausted T cells retain effector gene signatures, a feature that is associated with expression of KLRs (killer lectin-like receptors). Although KLR T cells may improve control of chronic antigen, the signaling molecules regulating this population are poorly understood. Using scRNA-seq, flow cytometry, RNA velocity, and scTCR-seq, we demonstrate that deleting the pseudokinase Trib1 shifts T towards CX3CR1 intermediates (T ) with robust enrichment of KLR CD8 T cells (T ) via clonal T cell expansion. These changes are associated with globally increased KLR gene expression throughout the exhaustion program. Further, Trib1 loss augments anti-PD-L1 blockade to improve viral clearance by expanding the T population. Together, these data identify Trib1 as an important regulator of T cell exhaustion whose targeting enhances the KLR effector state and improves the response to checkpoint inhibitor therapy.